A script to install Chrome OS recovery image for Pixelbook to USB stick.

cros2usb

#!/bin/bash

#   repo: https://gist.github.com/libredot/4b7c36d7682a9fdbc00e682ea2936eaa
# author: libredot@gmail.com

set -ex
if [[ ! -b ${1} ]]; then
        echo "Usage: ${0} /dev/sdx"
        exit 1
fi

# If we're not running as root, restart as root.
if [[ ${UID:-$(id -u)} -ne 0 ]]; then
  exec sudo "${0}" "${@}"
fi

# stop auto-mounting USB devices
stop cros-disks || :

SCRIPT_FULL_PATH="$(readlink -f "${0}")"
SCRIPT_ROOT=$(dirname ${SCRIPT_FULL_PATH})
USB="${1}"
STATE="${USB}1"
ROOT_A="${USB}3"
ROOT_B="${USB}5"
BOOT="${USB}12"

# Download Pixelbook recovery image at first run
# IMG="chromeos_9901.77.0_eve_recovery_stable-channel_mp.bin"
IMG="chromeos_9901.77.0_squawks_recovery_stable-channel_mp-v4.bin"
URL="https://dl.google.com/dl/edgedl/chromeos/recovery/${IMG}.zip"

# TODO: document this
if [[ -n "${2}" ]]; then
  IMG="${2}"
fi

[[ -f ${SCRIPT_ROOT}/${IMG} ]] || curl ${URL} | zcat > ${IMG}

chromeos-install --yes --debug --skip_postinstall --skip_src_removable --skip_dst_removable --payload_image=${IMG} --dst=${USB} 

################ grub.cfg hacks ##################
# - Enable dev mode.
# - Fix PARTUUID.

PARTUUID_A="$(blkid "${ROOT_A}" | rev | cut -d ' ' -f 1 | rev | tr -d \" | tr '[a-z]' '[A-Z]')"
PARTUUID_B="$(blkid "${ROOT_B}" | rev | cut -d ' ' -f 1 | rev | tr -d \" | tr '[a-z]' '[A-Z]')"
BOOT_MNT="$(mktemp -d)"
mount "${BOOT}" "${BOOT_MNT}"
cat << EOF > "${BOOT_MNT}/efi/boot/grub.cfg"
set timeout=3
menuentry "local image A" {
  linux /syslinux/vmlinuz.A init=/sbin/init boot=local rootwait ro noresume noswap loglevel=7 noinitrd console=  i915.modeset=1 cros_efi cros_debug root=${PARTUUID_A}
}
menuentry "local image B" {
  linux /syslinux/vmlinuz.B init=/sbin/init boot=local rootwait ro noresume noswap loglevel=7 noinitrd console=  i915.modeset=1 cros_efi cros_debug root=${PARTUUID_B}
}
EOF
umount "${BOOT_MNT}"
rmdir "${BOOT_MNT}"

################ rootfs hacks ##################
# - Enable rw mount for root partition. 
#   To revert, '\000' -> '\777'
#   To show what changes are made, run:
#     dumpe2fs ${ROOT} | grep 'Filesystem features'
#   You are not supposed to understand this magic ;)
# - pstore.conf considered harmful. Get rid of it.

ROOT_MNT="$(mktemp -d)"
for ROOT in "${ROOT_A}" "${ROOT_B}"; do
  printf '\000' | dd of=${ROOT} seek=$((0x464+3)) conv=notrunc count=1 bs=1 status=none
  mount "${ROOT}" "${ROOT_MNT}"
  cp ${SCRIPT_FULL_PATH} ${ROOT_MNT}
  rm "${ROOT_MNT}/etc/init/pstore.conf"
  mv ${ROOT_MNT}/usr/bin/crosh{,-bak}
  mv ${ROOT_MNT}/sbin/chromeos_startup{,-bak}
cat << EOF > "${ROOT_MNT}/etc/shadow"
root:*:::::::
chronos:*:::::::
EOF
cat << EOF > "${ROOT_MNT}/usr/bin/crosh"
#!/bin/bash
exec sudo su - chronos
EOF
cat << EOF > "${ROOT_MNT}/sbin/chromeos_startup"
#!/bin/bash
mount -t debugfs none /sys/kernel/debug
bootstat pre-startup
mkdir -p /dev/pts /dev/shm
mount -n -t tmpfs shmfs /dev/shm
mount -n -t devpts -o noexec,nosuid,gid=5,mode=0620 devpts /dev/pts
sysctl -q --system

mount "/dev/$(lsblk -n -o pkname $(findmnt -n -o source /))1" /mnt/stateful_partition

mkdir -p /mnt/stateful_partition/dev_image
mkdir -p /mnt/stateful_partition/var_overlay
mkdir -p /mnt/stateful_partition/etc/docker
mount --bind /mnt/stateful_partition/dev_image /usr/local
mount --bind /mnt/stateful_partition/var_overlay /var

for d in home home/chronos home/root home/user unencrypted unencrypted/cache unencrypted/preserve; do
  mkdir -p -m 0755 "/mnt/stateful_partition/${d}"
done
mount --bind /mnt/stateful_partition/home /home
rm -rf /var/run /var/lock
ln -s /run /var/run
ln -s /run/lock /var/lock
mkdir -p -m 0755 /var/cache /var/db /var/empty /var/log/metrics /var/spool /var/tmp /var/lib/misc
chmod 1777 /var/tmp
chmod 1771 /home/root
chown chronos:chronos /home/chronos /var/log/metrics
chgrp syslog /var/log
chmod 1775 /var/log
chmod 0755 /var/cache /var/db /var/empty /var/spool /var/lib /var/lib/misc
chattr +i /var/empty || :
mount --make-shared -n -t tmpfs media /media
bootstat post-startup
exit 0
EOF
  umount "${ROOT_MNT}"
done
rmdir "${ROOT_MNT}"

echo "OK. Now please shutdown and reboot."